For a long time, culture dishes and flasks have been used for microorganism, cell and tissue culture. Culture dishes consist of a bottom dish to contain medium for cell growth and a removable cover. Although the removable cover provide a convenient access, cells are often contaminated by other microorganisms while the cover is removed during culture operation. To solve this problem, culture flasks were developed. The culture flasks typically have a culture chamber, a small tubular opening located on one side of the flask and a corresponding screw-on closure. This design prevents direct exposure of cells to dust, bacteria and yeast. Cell contamination is largely reduced. The screw-on closure and tubular opening are widely used in all flasks including prior arts (U.S. Pat. Nos. 4,334,028; 4,851,351 and 5,398,837).
Although application of the small tubular opening resolves the problem of contamination, a complication of the small opening causes a major difficulty for culture operations, such as insertion of a pipette through the opening for applying culture media. An inaccessible area is created in the culture chamber, particularly on the area adjacent to the opening. The problem becomes more severe during operations such as scraping cells off the flask, picking up colonies where they develop during culture process. Carver (U.S. Pat. No. 4,334,028) attempted to solve this problem by introducing a frangible zone on top of the flask. Culture procedures are accomplished through the opening on top of the flask created by cutting or breaking the frangible zone. When these flasks are used, cells are potentially contaminated through the broken wall. In addition, extra equipment and effort are also required to create the opening.
Cell culture procedure is a time-consuming manual operation. Generally it takes much longer time to accomplish when flasks are used for these problems related to the small tubular opening and closure. First, it consumes a longer time to perform all culture procedures through the small tubular opening. Second, the screw-on closure is usually required to be hold in a hand in order to avoid the closure being contacted with other objects and contaminated. A user has to perform culture procedures with a single hand. Consequently, these factors greatly reduce culture operation efficiency.